This application is part of an ongoing effort to study the mechanical properties of the ear. The development of two methods of measurements, laser interferometry and time-averaged holography, permits us to measure, at submicroscopic levels, either displacements and their phases at selected places or patterns distributed in space at higher, but still submicroscopic, levels. That is to say, compared to other methods available at present, the interferometric method is more sensitive, by several order of magnitude, and is thus capable of measuring responses to sound pressures within the physiological range. With the aid of these methods, measurements will be made on basilar membrane displacements. Data thus obtained will be compared to those provided by other methods and various hypotheses of mechanical cochlear function will be tested against them. Before devoting all of our attention to the inner ear we would like to complete two middle-ear studies: (1) a qualitative assessment of force transformation and (2) a re-assessment of inner ear impedance.